Multi-store Developments within the UK Southern North Sea: Implications for Carbon Storage Pore Space Usage

Phase 1 of the NEP project aims to store up to an initial 4 Mt CO2 per annum for 25 years within the Bunter Sandstone Formation at the Endurance structure. Endurance will be the first of several CO2 stores planned to be operational within the same saline aquifer. Evaluation of the connected pore space and the potential for interference between multiple stores is therefore a critical element to consider. A regional model focused on the Silver Pit Basin hydraulic unit has been built to assess regional pressurisation from multi-store operations. Structural, sedimentological and petrophysical interpretations were combined to create a regional aquifer scale 3D geocellular model. Dynamic time-step simulations were run in Nexus and PFLOTRAN-OGS to characterise the performance of CO2 injection and regional pressurisation within the hydraulic unit. The dynamic simulation modelling identified aquifer connectivity/permeability as a fundamental factor for controlling pressure dissipation. The ability for pressure to dissipate is ultimately a key driver for maximising available storage capacity, as pressure interference between multiple store developments may result in injection rate curtailments to manage operating pressure limits. A multi-store integrated development scheme allows scope for flexibility to manage pressure development within the wider hydraulic unit.